issue28032: never imply --with-lto as part of --with-optimizations.

Too many build tool chains do not properly support it, including building
and linking an executable fine that simply segfaults when you try to run
it (such as debian jessie 8.5's gcc 4.9).  On others where it does appear
to build (ubuntu 16.04's gcc 5.4) there are still test_distutils and test_gdb
failures to deal with.

We're not going to spend time attempting to maintain a complicated white list
of what does and doesn't work in our configure.ac file.

1 files changed, 5 insertions, 8 deletions

diff --git a/configure b/configure
index 04b1968..8c1650c 100755
--- a/configure
+++ b/configure
@@ -1510,7 +1510,7 @@ Optional Packages:
                           compiler
   --with-suffix=.exe      set executable suffix
   --with-pydebug          build with Py_DEBUG defined
-  --with-optimizations    Enable all optimizations when available (LTO, PGO,
+  --with-optimizations    Enable expensive optimizations (PGO, maybe LTO,
                           etc). Disabled by default.
   --with-lto              Enable Link Time Optimization in PGO builds.
                           Disabled by default.
@@ -6495,13 +6495,10 @@ $as_echo "no" >&6; }
 fi
 
 if test "$Py_OPT" = 'true' ; then
-  Py_LTO='true'
-  case $ac_sys_system in
-    Darwin*)
-      # At least on macOS El Capitan, LTO does not work with PGO.
-      Py_LTO='false'
-      ;;
-    esac
+  # Intentionally not forcing Py_LTO='true' here.  Too many toolchains do not
+  # compile working code using it and both test_distutils and test_gdb are
+  # broken when you do managed to get a toolchain that works with it.  People
+  # who want LTO need to use --with-lto themselves.
   DEF_MAKE_ALL_RULE="profile-opt"
   REQUIRE_PGO="yes"
   DEF_MAKE_RULE="build_all"